1. Field of the Invention
The present invention relates to a method of, and an apparatus for exchanging a die holder mounted on an extrusion head of an extruder.
2. Description of Related Art
Conventionally, for exchanging a die holder that is tightly pressed against the lower surface of an extrusion head by a press member, the press member is separated from the extrusion head and the used die holder is then dropped down and thereby detached from the extrusion head. Subsequently, a next die holder is delivered to a predetermined position at the lower surface of the extrusion head, and brought into contact with the lower surface and tightly pressed by the press member from the bottom.
The above-mentioned conventional method suffers from time-consuming operations and, hence, unsatisfactory work efficiency and productivity. This is because the detaching operation of the used die holder and the attaching operation of the next die holder are conducted separately, besides that the positioning of the next die holder relative to the extrusion head is not an easy operation in that it must be conducted while supporting the considerably heavy die holder from the bottom.
It is therefore an object of the present invention to provide improved die-holder exchanging method and apparatus, capable of readily exchanging a die holder in a short time and with higher work efficiency.
According to one aspect of the present invention, there is provided a method for exchanging a die holder of an extruder, which is tightly pressed from the bottom against a lower surface of an extrusion head by a press member, said method comprising the steps of (i) reducing the pressing force of said press member to thereby form a gap between the used die holder and said extrusion head; (ii) simultaneously and longitudinally moving the used die holder and a next die holder positioned collinearly with each other while slidingly contacting both of these die holders with said press member, so as to eject the used die holder from said press member and to deliver the next die holder onto said press member; and (iii) tightly pressing the next die holder from the bottom onto the lower surface of said extrusion head by said press member.
According to another aspect of the present invention, there is provided an apparatus for exchanging a die holder of an extruder, which is tightly pressed from the bottom against a lower surface of an extrusion head by a press member, said apparatus comprising (i) gap forming means for reducing the pressing force of said press member to thereby form a gap between the used die holder and said extrusion head; and (ii) moving means for simultaneously and longitudinally moving the used die holder and a next die holder positioned collinearly with each other while slidingly contacting these die holders with said press member, so as to eject the used die holder from said press member and deliver the next die holder onto said press member.
In exchanging the die holder of an extruder, according to the present invention, the gap forming means is first of all operated to reduce the pressing force that is being applied onto the used die holder by the press member, to thereby form a gap between the extrusion head and the used die holder. Then, the used die holder and a next die holder positioned collinearly with each other are simultaneously and longitudinally moved by the moving means, so as to eject the used die holder from the press member and deliver the next die holder onto the press member. In this way, the die holders are exchanged. At this time, both of the used die holder and next die holder are simultaneously moved, thereby allowing the exchange of the die holder in a short time to thereby improve the work efficiency and productivity.
Furthermore, in exchanging the die holder, the used die holder and the next die holder are moved simultaneously while slidingly contacting with the press member, i.e., while they are guided by the press member. Thus, the die holders are prevented from being moved in the widthwise direction. As a result, simply by operating the press member so as to press the next die holder from the bottom onto the extrusion head, the next die holder can be precisely and readily aligned with a predetermined position of the extrusion head in a short time to thereby further improve the work efficiency.
It is preferred that the die holder exchanging apparatus according to the present invention further comprises an adjusting mechanism for adjusting the gap amount between said extrusion head and the used die holder. In this instance, it is possible to readily and simultaneously smoothen the movement of the used and next die holders into the longitudinal direction, and to reduce the amount of the extrusion material to be left between the die holder and extrusion head.
It is also preferred that each die holder is provided with a scraper at its front end portion as seen in the moving direction thereof, so that the scraper is slidingly contacted with the lower surface of said extrusion head when the die holder is longitudinally moved. In this instance, it is possible to significantly reduce the amount of the extrusion material to be left between the extrusion head and die holder.
It is also preferred that the die holder exchanging apparatus according to the present invention further comprises storing means for storing a plurality of die holders to be used afterward, and transfer means for taking out die holders one by one from said storing means in accordance with the using order, and for transferring the taken out die holder to a position collinear with the used die holder. In this instance, it is possible to transfer a next die holder to a position collinear with the used die holder by an outside preparation during the extruding operation, so as to cause the next die holder to wait for the exchanging time, and thereby facilitate a rapid exchange of the die holders.